dmaengine: idxd: check GENCAP config support for gencfg register

DSA spec 1.2 has moved the GENCFG register under the GENCAP configuration
support with respect to writability. Add check in driver before writing to
GENCFG register.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163406171896.1303830.11217958011385656998.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/device.c

@@ -791,7 +791,7 @@ static int idxd_groups_config_write(struct idxd_device *idxd)
 	struct device *dev = &idxd->pdev->dev;
 
 	/* Setup bandwidth token limit */
-	if (idxd->token_limit) {
+	if (idxd->hw.gen_cap.config_en && idxd->token_limit) {
 		reg.bits = ioread32(idxd->reg_base + IDXD_GENCFG_OFFSET);
 		reg.token_limit = idxd->token_limit;
 		iowrite32(reg.bits, idxd->reg_base + IDXD_GENCFG_OFFSET);